fix undefined

cell/view/WorksheetView.js

@@ -2085,14 +2085,14 @@
     /** Рисует заголовки видимых колонок */
     WorksheetView.prototype._drawColumnHeaders =
       function (drawingCtx, start, end, style, offsetXForDraw, offsetYForDraw) {
-          if (undefined === drawingCtx && false === this.model.sheetViews[0].asc_getShowRowColHeaders()) {
+          if (null === drawingCtx && false === this.model.sheetViews[0].asc_getShowRowColHeaders()) {
               return;
           }
           var vr = this.visibleRange;
           var c = this.cols;
           var offsetX = (undefined !== offsetXForDraw) ? offsetXForDraw : c[vr.c1].left - this.cellsLeft;
           var offsetY = (undefined !== offsetYForDraw) ? offsetYForDraw : this.headersTop;
-          if (undefined === drawingCtx && this.topLeftFrozenCell && undefined === offsetXForDraw) {
+          if (null === drawingCtx && this.topLeftFrozenCell && undefined === offsetXForDraw) {
               var cFrozen = this.topLeftFrozenCell.getCol0();
               if (start < vr.c1) {
                   offsetX = c[0].left - this.cellsLeft;
@@ -2122,14 +2122,14 @@
 
     /** Рисует заголовки видимых строк */
     WorksheetView.prototype._drawRowHeaders = function (drawingCtx, start, end, style, offsetXForDraw, offsetYForDraw) {
-        if (undefined === drawingCtx && false === this.model.sheetViews[0].asc_getShowRowColHeaders()) {
+        if (null === drawingCtx && false === this.model.sheetViews[0].asc_getShowRowColHeaders()) {
             return;
         }
         var vr = this.visibleRange;
         var r = this.rows;
         var offsetX = (undefined !== offsetXForDraw) ? offsetXForDraw : this.headersLeft;
         var offsetY = (undefined !== offsetYForDraw) ? offsetYForDraw : r[vr.r1].top - this.cellsTop;
-        if (undefined === drawingCtx && this.topLeftFrozenCell && undefined === offsetYForDraw) {
+        if (null === drawingCtx && this.topLeftFrozenCell && undefined === offsetYForDraw) {
             var rFrozen = this.topLeftFrozenCell.getRow0();
             if (start < vr.r1) {
                 offsetY = r[0].top - this.cellsTop;
@@ -2335,7 +2335,7 @@
     /** Рисует сетку таблицы */
     WorksheetView.prototype._drawGrid = function ( drawingCtx, range, leftFieldInPt, topFieldInPt, width, height ) {
         // Возможно сетку не нужно рисовать (при печати свои проверки)
-        if ( undefined === drawingCtx && false === this.model.sheetViews[0].asc_getShowGridLines() ) {
+        if ( null === drawingCtx && false === this.model.sheetViews[0].asc_getShowGridLines() ) {
             return;
         }
 
@@ -2349,7 +2349,7 @@
         var heightCtx = (height) ? height : ctx.getHeight();
         var offsetX = (undefined !== leftFieldInPt) ? leftFieldInPt : c[this.visibleRange.c1].left - this.cellsLeft;
         var offsetY = (undefined !== topFieldInPt) ? topFieldInPt : r[this.visibleRange.r1].top - this.cellsTop;
-        if ( undefined === drawingCtx && this.topLeftFrozenCell ) {
+        if ( null === drawingCtx && this.topLeftFrozenCell ) {
             if ( undefined === leftFieldInPt ) {
                 var cFrozen = this.topLeftFrozenCell.getCol0();
                 offsetX -= c[cFrozen].left - c[0].left;
@@ -2395,7 +2395,7 @@
         var left, top, cFrozen, rFrozen;
         var offsetX = (undefined === offsetXForDraw) ? this.cols[this.visibleRange.c1].left - this.cellsLeft : offsetXForDraw;
         var offsetY = (undefined === offsetYForDraw) ? this.rows[this.visibleRange.r1].top - this.cellsTop : offsetYForDraw;
-        if ( undefined === drawingCtx && this.topLeftFrozenCell ) {
+        if ( null === drawingCtx && this.topLeftFrozenCell ) {
             if ( undefined === offsetXForDraw ) {
                 cFrozen = this.topLeftFrozenCell.getCol0();
                 offsetX -= this.cols[cFrozen].left - this.cols[0].left;